In the workup of a non-palpable, radiographic, and/or difficult to locate anatomic tissue (e.g., a lesion such as a tumor, wound, ulcer, abscess, etc. or even healthy tissue) in surgery, the location of this tissue is typically inked, tattooed, or physically oriented with needle/wires to direct the surgeon for excision or to monitor the tissue over time. Examples of lesions include, but are not limited to, neoplasms in the intestine, radiographic breast lesions, neurologic lesions, or soft tissue masses elsewhere in the body. Again, these lesions are either non-palpable, in a tissue location that is difficult to visualize, and/or have characteristics, such as lymph node drainage, that can make visualizing the tissue during surgery extremely difficult. Additionally, lymph nodes are often difficult to locate, visualize, and map.
Currently, carbon-based ink or radioactive agents are used by surgeons to mark tissue that is often difficult to visualize during surgery or to map lymph nodes during, for example, sentinel lymph node mapping. Nevertheless, carbon-based ink is often difficult to see, and radioactive agents put the patient at risk for radiation exposure. Moreover, while fluorescent inks or dyes have been utilized, the lack of stability and tendency of fluorescent inks to migrate to other areas outside the tissue or lymph nodes of interest have made their use problematic. For instance, surgeons may inject nano-sized fluorescent dye particles intravascularly with the hope that the particles will eventually reach the tissue of interest, such as cancerous tissue, due to the permeability changes of cells affected by cancer, thus allowing the particles to enter the tissue. However, such small particles often degrade with time and can also migrate out of the area of interest. Furthermore, such small particles often require coating with a surfactant or protein in an attempt to limit the degradation of the particles and/or concentrate or direct the particles to the tissue of interest. As such, a need exists for effective tattooing for the visualization of non-palpable tissue and/or lymph nodes that does not degrade, that does not migrate, and that can be directly injected into the tissue of interest. In other words, a need exists for a fluorescent ink or dye for marking tissue (e.g., healthy tissue or lesions) or lymph nodes of interest that is stable, exhibits minimal degradation, and does not migrate once it is introduced to the tissue or lymph node of interest.